This application claims the priority benefit of Taiwan application serial no. 89117742, filed Aug. 31, 2000.
1. Field of Invention
The present invention relates to a detector for checking the condition of a silicon chip undergoing chemical-mechanical polishing. More particularly, the present invention relates to a detector capable of sensing any scratching or chipping of the silicon chip during chemical-mechanical polishing.
2. Description of Related Art
Chemical-mechanical polishing (CMP) is a global planarization technique in very-large scale integration (VLSI) or ultra-large scale integration (ULSI). The technique utilizes a grinding wheel, a chemical reagent or mixture of reagents for mechanically removing the top bumpy surface layer off a silicon chip.
FIG. 1 is a schematic cross-sectional view of the elements of a conventional chemical-mechanical polishing station necessary for carrying out a chip planarization. As shown in FIG. 1, the elements in the conventional chemical-mechanical polishing station include a polishing table 10 and a holder 16. The holder 16 is used to grasp the back surface of a silicon chip 14. To carry out chemical-mechanical polishing, the front surface of the silicon chip 14 is pressed against a polishing pad 12 on the upper surface of the polishing table 10.
During a CMP operation, both the polishing table 10 and the holder 16 will rotate at a pre-defined direction and a delivery tube will supply a chemical reagent to the polishing table 10 continuously. In other words, the CMP is a polishing process that utilizes chemical action of the chemical agent as well as the grinding action on the polishing table 10 to remove any protrusions on the upper surface of chip 14.
In the process of planarizing a silicon chip by CMP, some pollutants may drop on the polishing table resulting in severe scratching or chipping of the chip. A conventional polishing station has no monitoring system for detecting any serious scratching or chipping. Without any monitoring system for sounding an alarm or halting the polishing station, the offensive pollutants may remain undetected for quite some time. Since most processing operations are carried out in a continuous basis, by the time scratches or chipping of the chip are found, a large batch of silicon chips may have been produced. Hence, a large number of silicon chips has to be scrapped leading to great losses.
Accordingly, one object of the present invention is to provide a detecting device for finding any abnormality during a chemical-mechanical polishing operation so that any serious scratching or chipping of a silicon chip due to the presence of pollutant articles can be detected and removed in time to prevent a large batch of silicon chips all with defects are produced.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a detecting device for sensing any abnormality in chemical-mechanical polishing. The device includes a motor, an inverter, a control circuit, a sensor and a detector. The inverter converts a direct current into an alternating current for powering the motor. The control circuit controls size and functioning of the alternating output current from the inverter. The sensor is a transducer for converting the running speed of the motor into a rotation signal and transmitting the signal to the control circuit. The detector monitors the size of alternating current flowing from inverter to motor so that a system halt signal can be sent to the control circuit should any abnormality occur.
This invention also provides a second detecting device for finding any abnormality of a chemical-mechanical polishing operation. The detecting device includes a motor, an inverter, a control circuit, a rotation sensor, a current sensor, a relay controller and a chemical-mechanical controller. The inverter converts a direct current into an alternating current for driving the motor. The control circuit controls size and functioning of the output alternating current from the inverter. The rotation sensor is a transducer for converting the running speed of the motor into a rotation signal and transmitting the rotation signal to the control circuit. The current sensor monitors the size of the alternating current flowing to the motor and then outputs a current signal. The relay controller receives the current signal from the current sensor and outputs a drive signal. The chemical-mechanical polishing controller receives the drive signal from the relay controller and outputs a system halt signal to the control circuit.
The detecting device of this invention is able to detect any serious scratching or chipping of a silicon chip during chemical-mechanical polishing. This is possible because any extraordinary stress on the polishing station is indicated by the flow of an abnormal current in the electrical system. By sensing any abrupt variation of current in the electrical system, any pollutant particles that damage the silicon chip can be found and removed immediately.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.